Chapter 8 Gravitation Handwritten Notes Class 11 notes Physics

Chapter 8 Gravitation Class 11 notes Physics

Summary

• Gravitational force: It is a force of attraction between the two bodies by the virtue of their masses.
• Acceleration due to gravity: The acceleration produced in the motion of a body freely falling towards earth under the force of gravity is known as acceleration due to gravity.
• Gravitational potential energy: The amount of work done in displacing the particle from infinity to a point under consideration.
• Gravitational potential: The gravitational potential due to the gravitational force of the earth is defined as the potential energy of a particle of unit mass at that point.
• Escape speed: The minimum speed with which the body has to be projected vertically upwards from the surface of the earth is called escape speed.
• Orbital speed: The minimum speed required to put the satellite into the given orbit around earth is called orbital speed.
• Satellite: It is a body which revolves continuously in an orbit around a comparatively much larger body.
• Polar satellite: It is the satellite which revolves in polar orbit around the earth.
• Geostationary satellite: It is the satellite which appears at a fixed position and at a definite height to an observer on earth.
• Kepler’s Ist law: All planets move in elliptical orbits, with the sun at one of foci of the ellipse.
• Kepler’s IInd law: The line that joins any planet to the sun sweeps out equal areas in equal intervals of time.
• Kepler’s IIIrd law: The square of the time period of revolution of a planet is proportional to the cube of the semi-major axis of the ellipse traced out by the planet.
• Newton’s universal law of gravitation: Every particle in the universe attracts every other particle with a force which is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.
• Gravitational force is a conservative force.
• The value of acceleration due ot gravity is maximum at the surface of the earth while zero at the centre of earth.
• Henry Cavendish was the first person who found the value of G experimentally.
• Gravitational force on a particle inside a spherical shell is zero.
• Gravitational shielding is not possible.
• An astronaut experiences weightlessness in a space satellite. It is because both the astronaut and the satellite are in “free fall” towards the earth.
• The value of g increases from equator to poles.
• The escape speed from a point on the surface of the earth may depend on its location on the earth e.g., escape speed is more on poles and less on equator.
• The orbital speed of satellite is independent of mass of the satellites.
• Kepler’s laws hold equally well for satellites.